Hazard Estimation of Deep Seated Mass Movements by Microseismic Monitoring

Abstract

The task of the ISDR-20 (TUW - Vienna University of Technology) and ISDR-21 (TUG – Graz University of Technology) projects is the integration of geodetic and geophysical monitoring into a uniform surveillance system for deep-seated mass movements. The combination of continuous GPS measurements, high resolution strain meter observations, and a local seismic monitoring network should lead into an Integrated Monitoring System (IMoS). Seismic monitoring yields information on fracture and stick-slip phenomena caused by the mass movement, the strain meter will monitor local strain changes, and GPS measurements result in the medium to long term trend of surface displacements. Another aspect of GPS and broad band seismic monitoring is the coverage of the whole spectrum of movement, which ranges from quasi-continuous displacement via stick-slip to critical fracture. The combination of the two methods offers the opportunity to monitor displacements over a very broad frequency band from periods of seismic waves (~1/100 second) via short-time oscillation (minutes to hours) to long-time trends (several years). Interpretation of IMoS data will be based on structural models of the mass movements, developed by earlier projects within IDNDR and ISDR. The development of IMoS is in tight cooperation with Prof. F.K. Brunner, TUG. The test site is the well-investigated deep-seated mass movement Gradenbach. Another seismic monitoring campaign has been accomplished at Niedergallmig/Matekopf (Tirol) in cooperation with alpS (project A.2.4). This cooperation includes the sharing of seismic equipment and scientific data. For the seismic monitoring tasks, cooperation with Dr. M. Joswig, Institute of Geophysics, University of Stuttgart, has already been established. E. Bruckl had the opportunity of a two weeks stay at Niigata University, Japan, and to participate also INTERPRAEVENT 2006 in September 2006. A paper covering the essential results of seismic monitoring within ISDR-20 was presented (Bruckl and Mertl, 2006) and a special report covering experiences and new ideas developed during this visit was already sent to OAW. In July 2007 E. Bruckl was invited to present a paper at the 11th congress of the International Society for Rock Mechanics at Lisbon, Portugal. The paper describes the current progress in event detection and localization of microseismic events on deep-seated mass movements gained within the ISDR-20 project (Mertl and Bruckl, 2007).